Kinetic energy impact less-lethal projectiles have been in use for over 30 years. The early less-lethal projectiles were square cloth bags or sacks filled with No. 9 lead shot. They were commonly called “bean bags”. There were two sizes, a 12 gauge shotgun round containing 40 grams of lead shot and a 37 mm size containing 150 grams of lead shot. These projectiles were fired at a muzzle velocity of 230 and 300 feet per second (fps), for the shotgun, and from 110 to 250 feet per second (depending on the range) for the 37 mm rounds. The muzzle kinetic energy was about 70 and 120 ft-lbs, for the shotgun and from 70 to over 320 ft-lbs for the 37 mm projectiles.
These projectiles were widely used by the law enforcement community after it was demonstrated by experiment that the energy delivered by the impact was below the level determined to be lethal by blunt trauma impact to the heart area. The bags were rolled up inside the shotshell of the 12 ga. shotgun, and they begin to unroll at about 20 feet from the muzzle. When the bags impacted at less than the unrolling distance, the area of contact was reduced to less than 1 inch, thus raising the energy per unit area to the point where the bag could penetrate the body.
In the late 1990's a new form of bag was introduced, an aerodynamically shaped, drag stabilized projectile, U.S. Pat. No. 6,202,562, to Brunn et al. The “sock bag” as it became known, was fabricated from a coarsely woven fabric in the shape of a tube, hence the name, and was filled with # 9 lead shot and tied with a string to form the bag, leaving a tail to act as a stabilizer. This design gave a uniform impact signature as it collapsed on impact as opposed to the variable impact of a square bag, which varied from a cylindrical impact at minimal ranges, a rolled longitudinal strike at moderate ranges to a full, flat deployment at long ranges. This design proved to be more accurate than a square “bean bag”. However, the method of stabilization employed, limited the accuracy of the new design, due to variables in assembly of the projectile and post firing orientation.
A subsequent development introduced a foam projectile fired from a 40 mm launcher. This design abandoned the 12 gauge size in favor of the larger diameter impact area available from the larger diameter projectiles. The increased area of impact lowers the energy density and the compression of the foam nose lowers the sharpness of the impulse transmitted to the target individual at impact. A sharp impulse is more deleterious to tissue than a softer one.